The present invention relates to an improvement in a two-phase pulse signal generating circuit in which the time duration of the pulse signals at the output thereof varies in response to a control signal applied to the signal generating circuit.
A conventional two-phase pulse generator typically comprises, for example, a pulse generator for generating pulses of a predetermined frequency, a flip-flop circuit connected to the pulse generator and a pair of monostable multivibrators each connected to the respective output terminals of the flip-flop circuit, wherein the pulses having the predetermined frequency are applied to the flip-flop circuit to provide a two-phase trigger, one of which pulses is applied to the one of the monostable multivibrators and the other of which is applied to the other multivibrator, thereby generating two-phase pulse signals.
However, in the conventional two-phase pulse generator described above, since the flip-flop circuit and the monostable multivibrators are triggered by pulse signals, they are apt to malfunction due to pulse noise signals and accordingly, such a two-phase pulse generator is not suitable for use in an automotive vehicle which is subjected to various kinds of pulse noise signals.
It is, therefore, an object of the present invention to provide a two-phase pulse signal generating circuit which is not responsive to pulsed noise signals and is suitable for use in an automobile.
It is another object of the present invention to provide a two-phase pulse signal generating circuit in which a first reference signal which linearly increases and decreases at a predetermined cycle and a second reference signal which is inverted with respect to the first reference signal are respectively applied to a couple of comparators which compare the respective signals with a control signal to generate two-phase pulse signals, the time duration of which varies in response to the control signal.
It is a further object of the present invention to provide a two-phase pulse generator in which a first triangular wave signal is inverted to provide a second triangular signal and wherein the first and second triangular signals are respectively compared with a control voltage by a couple of comparators to provide two-phase pulse signals.
It is a still further object of the present invention to provide a closed loop oscillator comprising a Schmitt circuit and an integrator circuit in which the frequency of the triangular wave signal is changed merely by changing a bias voltage.